[syslinux] Makefiles: includes and rule prerequisites

[Gene Cumm]

1) mk/syslinux.mk runs a shell to make a temp file gcc_ok.$$$$.tmp
(perhaps in the wrong directory) while several Makefiles have an
include rule for *.tmp which I believe is causing some occasional
parallel build issues.

make[3]: Entering directory `/home/gene/s/g/bios/memdump'
gcc_ok.6333.tmp:1: warning: NUL character seen; rest of line ignored
gcc_ok.6333.tmp:1: *** missing separator.  Stop.
make[3]: Leaving directory `/home/gene/s/g/bios/memdump'
make[2]: *** [memdump] Error 2


2) For recursive prerequisites, is it better to list the directory as
a prerequisite (simple and current approach) or would it be better to
have a more complex set of rules like the following:

--In com32/Makefile:
lib/libcom32.c32 lib/libcom32min.a lib/libcom32core.a: lib
libutil/libutil.c32: libutil

--In com32/rosh/Makefile:
rosh.c32: lib/libcom32.c32 libutil/libutil.c32

-- 
-Gene